Remove PermissionBackend.*#user()

This commit removes the user() method from all PermissionBackend
subclasses. This method just encourages callers to pass around a
PermissionBackend when they really want to pass around a CurrentUser
and/or ChangeNotes.

Passing around heavy objects that represent a subsystem for the benefit
of getting smaller objects from it is an anti-pattern. We had this issue
at a larger scale with {Ref,Project,Change}Control that were often just
passed around to have a user and/or entity information. Removing the
user() methods should prevent that.

This refactoring also uncovered some wrongdoing that we already had in
the code as a direct result from passing PermissionBackends around (see
previous commit).

Removing user() comes at the (small) const that every PermissionBackend
has to implement #testCond by itsself, which seems fair and like a
better pattern in general.

Change-Id: Ibae1fc25e51228dca2acaf0faec76beee539da01

java/com/google/gerrit/server/permissions/FailedPermissionBackend.java

@@ -15,6 +15,7 @@
 package com.google.gerrit.server.permissions;
 
 import com.google.gerrit.extensions.api.access.GlobalOrPluginPermission;
+import com.google.gerrit.extensions.conditions.BooleanCondition;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.server.ReviewDb;
@@ -83,11 +84,6 @@ public class FailedPermissionBackend {
       this.cause = cause;
     }
 
-    @Override
-    public CurrentUser user() {
-      throw new UnsupportedOperationException("FailedPermissionBackend is not scoped to user");
-    }
-
     @Override
     public ForProject project(Project.NameKey project) {
       return new FailedProject(message, cause);
@@ -103,6 +99,12 @@ public class FailedPermissionBackend {
         throws PermissionBackendException {
       throw new PermissionBackendException(message, cause);
     }
+
+    @Override
+    public BooleanCondition testCond(GlobalOrPluginPermission perm) {
+      throw new UnsupportedOperationException(
+          "FailedPermissionBackend does not support conditions");
+    }
   }
 
   private static class FailedProject extends ForProject {
@@ -119,11 +121,6 @@ public class FailedPermissionBackend {
       return this;
     }
 
-    @Override
-    public CurrentUser user() {
-      throw new UnsupportedOperationException("FailedPermissionBackend is not scoped to user");
-    }
-
     @Override
     public ForProject user(CurrentUser user) {
       return this;
@@ -156,6 +153,12 @@ public class FailedPermissionBackend {
       throw new PermissionBackendException(message, cause);
     }
 
+    @Override
+    public BooleanCondition testCond(ProjectPermission perm) {
+      throw new UnsupportedOperationException(
+          "FailedPermissionBackend does not support conditions");
+    }
+
     @Override
     public Map<String, Ref> filter(Map<String, Ref> refs, Repository repo, RefFilterOptions opts)
         throws PermissionBackendException {
@@ -177,11 +180,6 @@ public class FailedPermissionBackend {
       return this;
     }
 
-    @Override
-    public CurrentUser user() {
-      throw new UnsupportedOperationException("FailedPermissionBackend is not scoped to user");
-    }
-
     @Override
     public ForRef user(CurrentUser user) {
       return this;
@@ -223,6 +221,12 @@ public class FailedPermissionBackend {
         throws PermissionBackendException {
       throw new PermissionBackendException(message, cause);
     }
+
+    @Override
+    public BooleanCondition testCond(RefPermission perm) {
+      throw new UnsupportedOperationException(
+          "FailedPermissionBackend does not support conditions");
+    }
   }
 
   private static class FailedChange extends ForChange {
@@ -267,8 +271,9 @@ public class FailedPermissionBackend {
     }
 
     @Override
-    public CurrentUser user() {
-      throw new UnsupportedOperationException("FailedPermissionBackend is not scoped to user");
+    public BooleanCondition testCond(ChangePermissionOrLabel perm) {
+      throw new UnsupportedOperationException(
+          "FailedPermissionBackend does not support conditions");
     }
   }
 }